1. FIELD OF THE INVENTION
This invention relates to an improvement in a high voltage generating device utilizing a piezoelectric transformer.
2. DESCRIPTION OF THE PRIOR ART
For example, a black-and-white television receiver requires a high voltage of the order of 10,000 to 15,000 volts to make the cathode-ray tube luminant. Conventional television receivers employ a flyback transformer for the generation of such a high voltage. The flyback transformer which is based on the principle of a winding-type transformer, has several thousands of turns of very fine copper wire having a diameter of the order of 0.1 mm wound around a ferrite core and has undergone an insulating process so as to withstand the above-mentioned high voltage. The flyback transformer, accordingly, is considerably complicated in shape and relatively large in size and weight.
Therefore, it is very desirable if the winding can be eliminated from such a transformer and a windingless flyback transformer provided. To meet such a demand, a novel principle had to be exploited which replaces the conventional voltage conversion method based on the principle of electric-to-magnetic-to-electric energy conversion.
With the advent of ceramic piezoelectric materials, a novel idea has been conceived which utilizes the piezoelectric effect of such a material to achieve the desired voltage conversion by means of an electric-to-mechanical-to-electric conversion of energy, finally leading to the development of the piezoelectric transformer.
A piezoelectric transformer was first proposed by C. A. Rosen et al who applied for a patent in 1954 and was granted the patent in 1958 (see U.S. Pat. No. 2,830,274). C. A. Rosen et al. described the piezoelectric transformer as an outstandingly useful means for generating a high voltage. Since then, however, no further practical development has been seen in the field of the piezoelectric transformer other than verificaton tests and theoretical analysises of the principle, because of various technical problems still to be overcome.